Expression of CD39 and CD73 proteins and mRNA in isolated human B cells. (A) Flow cytometry shows coexpression of CD39 and CD73 in the CD19⁺, CD4⁺, CD39⁺, and CD39^neg subsets of human lymphocytes. Percentages of positive cells are indicated in relevant quadrants. (B) Confocal images of CD19⁺ B cells coexpressing CD39 and CD73. Magnification ×100. (C) The MFI values for surface expression of the 2 ectonucleotidases are higher in B cells than CD4⁺ T cells. Data are means ± standard deviation determined for all CD4⁺ T cells and CD19⁺ B cells. The cells were obtained from 5 normal donors. (D) Western blots of freshly isolated human CD19⁺ B cells. (E) RT-PCR results for CD39 and CD73 mRNA expression in the isolated subsets of human peripheral blood T cells and CD19⁺ B cells. B cells express significantly higher levels of mRNA specific for CD39 and CD73 as compared with various T-cell populations. The data are mean relative levels ± standard deviation from 3 independent experiments with cells of different donors.